1. Field of the Invention
The present invention relates to a novel cinnamaldehyde compound having an azido group. The compound is useful as an intermediate for providing a photosensitive moiety of a photoresist, and also as the photosensitive moiety.
2. Description of the Related Art
Azide-based photoresists find a variety of uses, by virtue of offering a wide range of adaptability, low cost, and high resolution.
Among azide compounds conventionally used for providing such photoresists, disodium 4,4xe2x80x2-diazidostilbene-2,2xe2x80x2-disulfonate is known to be a typical azide compound.
Photoresists produced from such an azide compound show remarkably high sensitivity to light of a wavelength of 300 to 360 nm. However, in order to further enhance sensitivity of photoresists, an azide compound showing its light absorption band in a longer wavelength region has been desired.
In this connection, there have been proposed water-soluble diazide compounds which are synthesized through condensation of, for example, sodium 4-azidobenzaldehyde-2-sulfonate with an aliphatic ketone such as acetone or cyclohexanone. For example, Japanese Patent Application Laid-Open (kokai) No. 50-141403 discloses a diazide compound showing its light absorption band in a longer wavelength region.
Although the above-mentioned conventional water-soluble diazide compounds show their light absorption band which is red-shifted by reacting an azidobenzaldehyde compound with an aliphatic ketone or a similar compound, there has still remained a demand for further red-shifting the light absorption band.
Azidobenzaldehyde compounds, which are employed as raw materials for introducing a photosensitive unit to a variety of compounds, show its absorption maximum wavelength at about 290 nm. Since the wavelength range of the light absorption band of the introduced photosensitive unit is varied in accordance with the absorption maximum wavelength of the employed azidobenzaldehyde compound, the obtained wavelength region of the light absorption band is still unsatisfactory. Thus, a need exists to introduce a photosensitive unit showing its light absorption band in a further red-shifted wavelength region.
In view of the foregoing, the present inventor has carried out extensive studies on provision of a novel aldehyde compound having an azido group (hereinafter may be referred to as a novel azidoaldehyde compound), which compound, when used as an intermediate for providing a photosensitive moiety of a photoresist, introduces a photosensitive moiety having high sensitivity and attaining high contrast between the exposed portion and the unexposed portion, and which compound per se can also serve as a photosensitive moiety. The inventor has found that the aforementioned problems can be solved by an azidocinnamaldehyde compound produced through insertion of a double bond into an azidobenzaldehyde compound. The present invention has been accomplished on the basis of this finding.
Thus, an object of the present invention is to provide a novel azidocinnamaldehyde compound which can readily provide a photosensitive unit showing its light absorption band in a longer wavelength region.
Accordingly, the present invention provides an azidocinnamaldehyde compound represented by the following formula (I): 
wherein R represents a lower alkyl group such as a C1 to C4 alkyl group, preferably a linear-chain group, more preferably a methyl group or an ethyl group.
In formula (I), Y represents hydrogen or a sulfonate salt group. Here, a sulfonate salt group is represented by xe2x80x94SO3M, and M represents an alkali metal such as lithium, sodium, or potassium; or an ammonium compound such as ammonium, monoalkylammonium, dialkylammonium , trialkylammonium, or tetraalkylammonium, for example.
The novel azidocinnamaldehyde compound overcomes the aforementioned drawbacks of conventional azidobenzaldehyde compounds. Thus, when used as an intermediate for providing a photosensitive moiety of a photoresist, the compound introduces a photosensitive moiety having high sensitivity and attaining high contrast between the exposed portion and the unexposed portion, and the compound per se can serve as a photosensitive moiety.
The azidocinnamaldehyde compound of the present invention can be produced through, for example, condensation of an azidobenzaldehyde compound (II) with a lower alkylaldehyde (III) in accordance with the following reaction scheme. 
Examples of the azidobenzaldehyde compound (II) employed in the above reaction include 4-azidobenzaldehyde and sodium 4-azidobenzaldehyde-2-sulfonate. Examples of the lower alkylaldehyde (III) include propanal and butanal. Use of acetaldehyde is not preferred, since yield of the target product decreases considerably.
In one embodiment, the reaction represented by the above reaction scheme is carried out in a solvent mixture of water and a lower alcohol such as ethanol or isopropyl alcohol and in the presence of a base such as potassium hydroxide or sodium hydroxide. However, no particular limitation is imposed on the reaction conditions, and those generally employed for condensation reaction of carbonyl compounds can also be employed.
The thus-obtained azidocinnamaldehyde compound of the present invention represented by formula (I) is a novel compound which no literature has reported. The azidocinnamaldehyde compound shows its absorption maximum wavelength which is red-shifted as compared with that of the starting azidobenzaldehyde compound.
Accordingly, when the azidocinnamaldehyde compound of the present invention is used instead of a conventional azidobenzaldehyde compound for providing a corresponding photosensitive unit of a photoresist, a photosensitive compound showing its absorption maximum wavelength in a longer wavelength region can be produced.